Hardening of copper alloys



United States Patent Office 3,@54,671 Patented Sept. 18, 1962 Force NoDrawing. Filed Mar. 24, 1961, Ser. No. 98,276 6 Claims. (Cl. 75153) Thisinvention relates to a process for hardening copper alloys and to anovel copper alloy having superior mechanical properties.

The hardening of copper alloys in accordance with conventional quenchingtechniques has proved to be unsuitable. These alloys when subjected tothe high temperatures employed in such techniques become soft and retaintheir softness even after quenching. In a further attempt to producehardened copper alloys, specially formulated quenching baths have beensuggested and, to a limited degree, produce alloys which exhibit hightensile strengths. However, the presently available high tensilestrength copper alloys lack the high electrical and thermal conductivitycharacteristics necessary for use in high conductivity applications.

It is the primary object of this invention, therefore, to circumvent theabove described deficiencies of the prior art by providing a new andimproved copper alloy and a process for producing the same.

Another object of this invention is to provide a copper alloy havingsuperior tensile strength properties together with high electrical andthermal conductivity characteristics.

A further object of this invention is to provide a cop per alloyparticularly adapted for use in high conductivity applications.

Other objects, advantages, and features of this invention will becomereadily apparent to those skilled in the art upon consideration of thefollowing detailed disclosure thereof.

It has been found in accordance with this invention that the aboveobjects are accomplished by a melting and casting technique in which afine dispersion of thorium boride particles is produced in molten copperat which time the liquid copper is chill cast to its solid state inorder to retain a uniform dispersion of the particles throughout thesolid copper. The thorium boride particles neither settle nor floatbecause the density thereof approximates that of copper.

In a more specific aspect, the process for producing the novel copperalloys of this invention involves the following procedure. Pure copperis melted in a graphite crucible. Boron is then added to the moltencopper and the liquid alloy is homogenized by stirring. Preferably theboron is added in the form of a copper-boron master alloy, however, ifdesired, the boron may be added as a single constituent. Thorium, eitheras pure thorium or as a copper-thorium master alloy, is then added tothe liquid melt and the resulting mixture is stirred in order to allowthe following reaction to occur in the molten copper.

The bar under the symbols for thorium and boron indicates that these twoelements are in solution in the molten copper and the arrow, followingthe symbol for thorium boride, indicates that the thorium boride isprecipitated as individual solid particles uniformly dispersedthroughout the molten copper. The resultant alloy is then chill cast ina cast iron mold to retain the particles in the dispersed statepreviously produced in the liquid copper. The thorium and boron areadded in stoichiometric quantities such that the final alloy containsfrom about 1 percent to 4 percent thorium boride.

The following table further illustrates the principles of this inventionby presenting specific examples of the copper alloys together with anindication of their mechanical properties in the hot rolled condition ata temperature of 750 C. These alloys contain from 1 percent to 4 percentthorium boride with the balance being substantially all copper.

Composition RF Hard- Tensile Strength ness Percent 'IhBi Percent As CastTemp, Str., p.s.i.

Ou C.

l Balance.-. 44. 6 RT 38,000 700 9,100 800 5. 240 900 4, 310 2 do 64. 3RT 43, 300 4 do 59. 3 RT 44,000 800 8, 970 900 5, 970 975 5, 820

As can be seen by the above data, the dispersion hardened copper alloysof this invention are characterized by greater strength than thatexhibited by pure copper at both room and elevated temperatures. Inaddition, the thermal and electrical conductivity of these alloys isconsiderably higher than other high conductivity copper alloys ofcomparable strength. The superior heat conductivity of these alloystogether with their increased strength makes them especially amenablefor use in the fabrication of heat absorbing shield material. Thecombined elevated temperature strength proper-ties and high electricalconductivity of these copper alloys make them useful in the manufactureof various electrical components such as switches as well as weldingelectrodes which carry high electric currents.

Unless otherwise indicated, the term percent, as used in the instantspecification and appended claims, refers to percent by weight based onthe final alloy weight.

Although the present invention has been described with particularreference to specific embodiments thereof, the invention is not to beconsidered as limited thereto, but eludes within its scope suchmodifications and alterations as come within the appended claims.

What is claimed is:

1. A process for hardening copper alloys comprising the steps ofintroducing thorium and boron into a mass of liquid copper to produce amolten solution thereof, stirring said molten solution in order toeffectuate a reaction between said thorium and boron, precipitatingthorium boride particles as a product of said reaction, dispersing saidprecipitated particles throughout said liquid copper in a uniformmanner, cooling said liquid copper to a sold state in order to retainsaid preciptated particles in a uniform dispersed manner.

2. A process in accordance with claim 1 wherein said thorium and boronare introduced in stoichiometric quantities such that said solid coppercontains from about 1 percent to 4 percent precipitated thorium borideparticles.

3. An improved copper alloy having superior tensile strength propertiesand high thermal and electrical conductivity characteristics consistingessentially of from about 1 percent to 4 percent thorium borideparticles uniformly dispersed throughout said alloy with the balance ofsaid alloy being substantially all copper.

4. An improved copper alloy having superior tensile strength propertiesand high thermal and electrical conductivity characteristics consistingessentially of about 1 percent thorium boride particles uniformlydispersed throughout said alloy with the balance of said alloy beingsubstantially all copper.

5. An improved copper alloy having superior tensile strength propertiesand high thermal and electrical conductivity characteristics consistingessentially of about 2 percent thorium boride particles uniformlydispersed throughout said alloy with the balance of said alloy beingsubstantially all copper.

6. An improved copper alloy having superior tensile strength propertiesand high thermal and electrical conductivity characteristics consistingessentially of about 4 percent thorium boride particles uniformlydispersed throughout said alloy with the balance of said alloy beingsubstantially all copper.

References Cited in the file of this patent UNITED STATES PATENTS Henselet a1 Dec. 24, Hensel et a1. Nov. 15, Silliman Apr. 2, Kelly Jan. 5,Bredzs et al. Sept. 30, Cooper Dec. 13,

FOREIGN PATENTS Canada Mar. 8,

In Interference N 0. 93,911 involvin g Patent N 0. 3,054,671, G J sky,Iardemng of copper alloys, final ju gment adverse S claims 1, 2, 3, 4, 5and 6 6 October 27, 196 4.]

ept. 16, 1964, as to fiicz'al Gazett Notice of Adverse Decision inInterference In Interference No. 93,911 involving Patent No. 3,054,671,G. J. London and S. Zirinsky, Hardening of copper alloys, final judgmentadverse to the patentees was rendered Sept. 16, 1964, as to claims 1, 2,3, 4, 5 and 6.

[Ofiioial Gazette October 27, 1.964.]

3. AN IMPROVED COPPER ALLOY HAVING SUPERIOR TENSILE STRENGTH PROPERTIESAND HIGH THERMAL AND ELECTRICAL CONDUCTIVITY CHARACTERISTIC CONSISTINGESSENTIALLY OF FROM ABOUT 1 PERCENT TO 4 PERCENT THORIUM BORIDEPARTICLES UNIFORMLY DISPERSED THROUGHOUT SAID ALLOY WITH THE BALANCE OFSAID ALLOY BEING SUBSTANTIALLY ALL COPPER.